1. Field of the Invention
This invention relates broadly to surgical devices and methods for the internal fixation of fractured bones, and more particularly to bone plates, fasteners and tools therefor.
2. State of the Art
Fractures of the distal tibia include tibial plafond (or pilon) fractures and ankle fractures. These “high energy” fractures are typically caused by axial loading of the ankle joint, due to falls, motor vehicle accidents and sports. The more common ankle fractures are usually repaired with screw fixation. However, as with any kind of intra-articular fracture, distal tibial fractures are notoriously difficult to treat and are associated with a high complication rate.
Tibial plafond fractures are relatively uncommon (less than one percent of all fractures). Still, several thousands of people suffer annually. The type of fracture depends on the degree of comminution and displacement. Treatments of plafond fractures include external fixation, plating and nailing.
The same four basic principles for internal fixation apply to the distal tibia fracture as for any other bone fracture. These principles are proper anatomic reduction, stable fixation, preservation of blood supply and early, active mobilization. Before plating the distal tibia, surgeons usually wait several days after the injury was incurred to allow the soft tissues to heal and the swelling to decrease. Normally they will plate the distal fibula immediately if it is also fractured. After plating the distal tibia, weight bearing is normally not allowed for several days.
Currently there is some controversy among orthopedic surgeons concerning the management of tibial plafond fractures as to whether to use internal plating or external fixation. The trend in recent years has shifted to external fixation due to complications associated with plating. Major complications include skin sloughing and infection. These relate to the significant soft tissue injury associated with the fracture. Other less common complications include non-union, malunion, osteoarthritis and arthrodesis.
Current plates have been developed to try to reverse that trend. The plates include Synthes LCP Anterolateral and Medial Distal Tibia Plates 3.5, Smith & Nephew Peri-Loc Anterolateral and Medial Tibia Locking Plates, and Zimmer Periarticular Distal Tibia Locking Plates. The current plates are made of stainless steel. While the plates are pre-contoured for a non-specific bone, the systems are provided with bending tools that can be extended through the holes of a respective plate or gripped pliers that externally hold the plate to effect additional bending of the plate. However, such bending must be done with the plate off the bone in a manner in which it is difficult to approximate the shape of the plate to a specific bone without significant trial and error. In addition, the medial plates of current distal tibia fixation systems have limited support for the subchondral bone of the articular surface. Moreover, any such support is either at a pre-determined fixed angle using fixed angle screws in threaded holes or variable angle and under compression. Where surgeons want to use a distal tibia plating system with a fixed angle construct to support the fracture, fixed angle constructs do not conform to the anatomy or have the required strength to support distal tibia fractures. Thus, these plate systems are unacceptable in their limitations. In addition, when attaching a bone plate to a fractured bone during an internal fixation procedure, surgeons often must select bone screws and/or pegs having sufficient length for bicortical engagement, yet not so long that the fastener tip extends through joint bearing surfaces or into soft tissues distal to the bone. Surgeons typically determine the appropriate bone screw length after drilling a hole into bone by: (1) removing the bone drill and inserting some type of depth gauge into the drilled hole, or (2) reading graduated indicia on either the bone drill or an ancillary device used in combination with the bone drill while the drill is still fully inserted into the drilled hole. The first approach normally is more time-consuming than the second. However the second approach typically involves the need for the surgeon to stoop over and peer into the surgical site in order to read indicia on the drill or ancillary device.